The United States' senior military leader has said that Nato would abide by its commitment to defend the three Baltic states should they be attacked, amid regional concerns over a newly assertive Russia.

Admiral Mike Mullen, chairman of the US joint chiefs of staff, said on Wedenesday: "Nato's commitment under Article Five for mutual defence is a very real commitment and it is one that Nato, I am confident, would stand up to."

Lithuania, Latvia and Estonia broke from the Soviet Union in 1991 and joined the Western military alliance in 2004.

The states remain wary of long-time dominant neighbour Russia, particularly after its conflict with Georgia in August.

US 'assurance'

Mullen made the comments in Lithuania's capital Vilnius at a news conference with Valdas Adamkus, the country's president.

"I certainly understand the reactions in places like Ukraine or the Baltics after what had happened in Georgia," Mullen said.

"And in part why I am here is... to reassure your countries, that the US is very committed to those obligations."

Mullen, who visited Latvia on Tuesday, said the US had "made that [reassurance to Baltic states] very clear" to General Nikolai Makarov, head of the Russian general staff, during a meeting in Helsinki this week.

The admiral said he saw a need for more joint military exercises with Baltic states, both in the Nato framework and bilaterally with Washington. 

The US has just taken over the rotating air police mission over the Baltic states, which have no fighter planes of their own.